• Energy Research

Proper management and treatment of municipal solid waste (MSW) plays a central role towards the reduction or elimination of uncontrolled disposal and the achievement of United Nations (UN) Sustainable Development Goals (SDGs) with the reduction of its vast adverse environmental and health impacts. Despite that, till now, there has never been a quantitative analysis of the progress in waste management infrastructure delivery worldwide. In this paper, we provide valuable insights regarding the progress in new MSW infrastructure delivery based on a dataset of 1764 projects from 156 countries, for the period 2014–2019. We also estimate the magnitude of uncontrolled waste disposal practices worldwide by estimating the gap between the current MSW infrastructure delivery and actual changes in MSW generation. Our results show that the new capacity delivered during the six years period amounted to 243 million metric tonnes (Mt) (40 million Mt per year), out of which 45% was delivered in high-income countries, 37.5% in the People’s Republic of China and 17.5% in the rest of the world, mainly through thermal treatment (~57%) and landfilling (8%). The average allocated per capita budget of these projects during this period is about US$14, equivalent to US$2.33 (cap*year)−1. Our main conclusion is that the share of uncontrolled disposal will continue to rise at least until 2028, reaching almost 730 million Mt per year. Evidently, the global community continues to face a serious challenge towards the implementation of the UN SDG 12, target 12.4 by 2020. The analysis demonstrates that infrastructure delivery must increase by four folds to eliminate uncontrolled disposal practices.

Thin-film photovoltaics (PV) cells offer several benefits over conventional first-generation PV technologies, including lighter weight, flexibility, and lower power generation cost. Among the competing thin-film technologies, chalcogenide solar cells offer promising performance on efficiency and technological maturity level. However, in order to appraise the performance of the technology thoroughly, issues such as raw materials scarcity, toxicity, and environmental impacts need to be investigated in detail. This paper therefore, for the first time, presents a cradle to gate life cycle assessment for four different emerging chalcogenide PV cells, and compares their results with copper zinc tin sulfide (CZTS) and the commercially available CIGS to examine their effectiveness in reducing the environmental impacts associated with PV technologies. To allow for a full range of indicators, life cycle assessment methods CML 2001, IMPACT 2002+, and ILCD 2011 were used to analyse the results. The results identify environmental hotspots associated with different materials and components and demonstrate that using current efficiencies, the environmental impact of copper indium gallium selenide (CIGS) for generating 1kWh electricity was lower than that of the other studied cells. However, at comparable efficiencies the antimony-based cells offered the lowest environmental impacts in all impact categories. The effect of materials used was also found to be lower than the impact of electricity consumed throughout the manufacturing process, with the absorber layer contributing the most to the majority of the impact categories examined. In terms of chemicals consumed, cadmium acetate contributed significantly to the majority of the environmental impacts. Stainless steel in the substrate/insulating layer and molybdenum in the back contact both contributed considerably to the toxicity and ozone depletion impact categories. This paper demonstrates considerable environmental benefits associated with non-toxic chalcogenide PV cells suggesting that the current environmental concerns can be addressed effectively using alternative materials and manufacturing techniques if current efficiencies are improved. Peer Reviewed

Kesterite-based structures are being extensively studied for solar module productions due to their earth abundant and nontoxic nature, high absorption coefficient, and a wide variety of scalable deposition methods. Kesterites are mostly manufactured using thin-film technology. However, in the last decade, the monograin approach has gained further attention, providing a third alternative to mono-crystalline wafer and thin film methods. This is due to its high throughput, low-cost deposition techniques, flexibility, and light weight. Despite the technical advancements in the monograin technology, their environmental impacts have not been studied in the literature. This paper, for the first time, presents a cradle to gate environmental life cycle assessment of CZTS monograin module production. The analysis is designed to identify the environmental hotspots associated with materials, energy usage, and manufacturing processes. The results were compared to CZTS thin-film and the commercially available CIGS technologies. The analyses suggested that the front contact accounted for the majority of impact in all categories due to the use of silver. The normalisation results showed that the marine aquatic ecotoxicity impact category dominated the overall impact results. A comparison of CZTS monograin and thin film production demonstrated that monograin outperformed the thin film technology when silver was substituted with alternative materials and was proximate to CIGS even considering their higher achieved efficiency. The analysis presents considerable environmental benefits associated with the monograin technology. Further savings in emissions could be achieved with improved conversion efficiency and usage of renewable energy sources in the manufacturing stages.

Starting from the specific entropy (SE) indicator, which is well exploited by ecologists for investigating the status of health and the development tendency of ecosystems, a specific entropy per amount of exergy gained (SEEG) was proposed in this study for assessing the intrinsic sustainability of systems in the technosphere. According to the SE, the lower the SEEG indicator, the higher the intrinsic sustainability of the investigated system. This indicator was used for assessing the intrinsic sustainability of the main waste management (WM) systems of the different EU27 member states (MS). The main findings demonstrate average values of SEEG of about 0.0026 and 0.009 for composting and recycling, respectively. For incineration and landfilling, SEEG was 1.310 and 1.333, respectively. This indicates that incineration activity has a lower intrinsic sustainability. Concerning WM systems, lower values of SEEG were detected for EU 27 MS with recycling and composting percentages of waste >55%. Therefore, the maximization of percentages of waste recycled and composted, as well as solid recovered fuel production, are preferred over incineration.

In this study, we examine the economic and environmental significance associated with the implementation of an EU waste-separated collection scheme in a developing context – Lebanon. Two scenarios, S1 and S2, representing different intensities of source segregation were analysed. In S1, the average source segregation intensity reached 25% and 13% for the Italian test area and Lebanese test area, respectively. In S2, source segregation intensity increased to 48% and 68% for the Italian and Lebanese test areas, respectively. Passing from S1 to S2 increased collection costs significantly, up to 44% with greater increases in the Italian test area where labour cost is higher. In both areas, environmental impacts decreased with greater source segregation intensity. Savings in the climate change impact and stratospheric ozone depletion potential were lower under the Lebanese test area in comparison with the Italian test area. In contrast, savings in freshwater eutrophication and acidification impact were lower for the Italian test area. The increase in the source segregation intensity resulted in maximum savings for the depletion of abiotic resources, 74% to 77% and 79% to 80% in a developing and developed context, respectively.

The environmental and energy performances of the Italian municipal solid waste incineration (MSWI) system was investigated by a life cycle assessment approach. On average the 39 MSWIs operating in Italy in 2018 treated about 6,000,000 Mg of residual municipal solid waste (RMSW) recovering on average from 448 kWh Mg−1 RMSW to 762 kWh Mg−1 RMSW of electricity and from 732 kWh Mg−1 RMSW to 1102 kWh Mg−1 RMSW of heat. The average quantity of CO2eq Mg−1 RMSW emitted ranged from about 800 up to about 1000 depending on the size and on the energy recovery scheme of the facility. Avoided impacts (i.e., negative values) were detected for the kg PM2,5eq Mg−1 RMSW and for human health (disability-adjusted life year Mg−1 RMSW). The determination of the hybrid primary energy index (MJ Mg−1 RMSW) indicated that mainly large size facilities and those operating according to a power and heat energy recovery scheme are effectively able to replace other primary energies by the exploitation of the lower heating values of the RMSW.